The flood damage has halted production of Carr’s water biscuits. A variety of other favourite names usually produced at the site have also been hit, including McVitie’s ginger nuts, Crawford’s custard creams and Crawford’s shortcake.

Several supermarkets said they were already running low on stocks of ginger nuts and some have already sold out of Carr’s water biscuits.

The factory in Caldewgate was inundated with 5ft of floodwater on 6 December. Owner United Biscuits said it would take several months to restart the brick ovens which give its water biscuits their distinctive taste and crunch. It said it had been unable to find alternative facilities elsewhere in the country to pick up production.

The biscuit manufacturer has placed newspaper adverts headed: “Flooding in water biscuit factory. Oh the irony.”

The ad said the factory had suffered significant damage and the heavy rain had “taken its toll on our community”.

A car is submerged under floodwaters in Carlisle city centre. Photograph: Andrew Yates/Reuters

Around 400 staff, contractors and suppliers are now working to get the factory back into full working order. Production on one line, McVitie’s Gold Bar, has restarted.

United Biscuits said: “Due to floods in Carlisle we are experiencing a shortage of a number products under the McVitie’s, Jacob’s, Carr’s and Crawford’s brands. We apologise if consumers are finding it difficult to get hold of some of these products and we are working hard at our Carlisle site to resume normal service as soon as possible.”

There had been fears that the business, which employs more than 600 people and is one of Carlisle’s biggest employers, would not be restarted because it had been also hit by flooding in 2005. It only reopened thanks to a £1m government grant.

Mike Heaney, factory general manager at United Biscuits, said: “Resuming factory production is a priority for us and our teams are well on track with this as our Gold Bar production has started. However we also recognise the importance of community at a time like this. Many of our employees have taken the time to support those most affected by the floods and keep spirits high, providing local rescue centres with supplies and carrying out local door-to-door biscuit drops.

“United Biscuits greatly appreciates the support that has been offered, and our thoughts remain with the thousands of people in Cumbria who have been impacted by the floods.”